Characterization of plasmon propagation in graphene on PZT substrates via infrared nano-imaging

Using scattering-type scanning near-field optical microscopy, we have characterized graphene plasmons on a graphene-lead zirconate titanate (PZT) back-gated structure. By applying modest back-gate voltages of $\pm$1 V across the PZT, we have been able to induce variations in the graphene plasmon wavelength of more than $\sim$200 nm. The change in plasmon wavelength we observe corresponds to a shift in carrier concentration in the graphene by more than one order of magnitude. Additionally, we describe the plasmonic losses originating from the presence of PZT in such a device. Our results also suggest that persistent tuning of the graphene plasmon may be achieved by utilizing the ferroelectric nature of PZT.